This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Titin is a mechanical protein (http://www.ks.uiuc.edu/Research/Categories/MechBio/) that protects muscle from overstretching, which can occur following a powerful muscle contraction. Defects in the titin gene have been correlated to muscular distrophy. Titin produces a restoring force when a muscle fiber is extended beyond its normal length. Much of what is understood about titin today arose from single-molecule experiments [1[unreadable]7] and computer simulations [8[unreadable]13] which have shed light on how the structure of titin resist mechanical stretching forces.